elm_ctxpopup: prevent a giant load of errors
i) There have been 2 sorts of errors, first the items have been deleted
after the list was deleted, thus the list items have already been destructed. which lead to the error as the popup items destroyed the list items on destruction as well.
ii) sd->box was attached to the ctxpopup when getting into group_del the
box has already been destroyed by the cleanup logic.
Subscribers: cedric, zmike
Differential Revision: https://phab.enlightenment.org/D6166
Reviewed-by: Cedric BAIL <email@example.com>